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PULVERISETTE 7
4.1.2
Number of Balls per Grinding Bowl
A larger number of balls reduces the grinding time, and the grinding result will
lie within a narrower grain band width.
Ball Ø
(mm)
Grinding
bowl volume
(ml)
12
45
5
Number of balls
(piece)
50
180 - 200
10
Number of balls
(piece)
6 - 8
18 - 20
15
Number of balls
(piece)
7
The number of balls should be observed to prevent attrition.
4.1.3
Calculated Ball Weight
5
10
15
Material
density
in g/cm³
Agate
2.65
0.17
1.39
4.68
Sintered corundum
3.8
0.25
1.99
6.72
Zirconium oxide
5.7
0.37
2.98
10.07
Stainless steel
7.8
0.51
4.08
13.78
Tempered steel
7.9
0.52
4.14
13.96
Hardmetal tungsten carbide
14.7
0.96
7.70
25.98
Silicon nitride (Syalon)
3.1
0.20
1.62
5.48
Ball diameter in mm
Calculated ball weight
in g
To calculate
the weight of the required balls, the “calculated ball weight” is mul-
tiplied by the “number” of balls needed.
Example: A 45 ml agate bowl must be filled with 185 agate balls of 5 mm diam-
eter.
Calculation: 0.17 g * 185 balls = 31.45 g
31.45 g of grinding balls can be weighed out and placed in the grinding bowl;
this saves the time required for counting out the balls.